Mobile terminals, such as cellular telephones, personal digital assistants (PDAs), tablet computers or the like commonly provide for access to a variety of networks and services. As such, many mobile terminals include a plurality of radio transceivers. By way of example, FIG. 1 illustrates multiple radio transceivers included within a mobile terminal that supports access to a long-term evolution (LTE) network, access to global positioning system (GPS) services and supports Bluetooth and/or Wi-Fi communications. As such, the mobile terminal of this example embodiment includes LTE base band circuitry 10, LTE radio frequency (RF) circuitry 12 and an antenna for transmitting and receiving LTE signals. Additionally, the mobile terminal of this example includes GPS base band circuitry 16, GPS RF circuitry 18 and an antenna 20 for transmitting and receiving GPS signals. Further, the mobile terminal of this example includes Bluetooth and/or Wi-Fi base band circuitry 22, Bluetooth and/or Wi-Fi RF circuitry 24 and an associated antenna 26 for transmitting and receiving Bluetooth and/or Wi-Fi signals.
As a result of the proximity of the plurality of radio transceivers, typically due to the relatively small form factor of the mobile terminal, in-device coexistence interference between the plurality of radio transceivers may be created, such as interference between the LTE signals, the GPS signals and the Bluetooth and/or Wi-Fi signals. In this regard, the proximity of the plurality of radio transceivers may allow for a situation in which the transmit power level of one transmitter is substantially greater than the received power level of another receiver. In order to mitigate against coexistence interference, filter technologies have been implemented, and frequency separation between the radio transceivers has been designed so as to avoid coexistence interference for at least some of the signals transmitted by the radio transceivers. However, there are certain coexistence scenarios, such as those involving different radio technologies that operate on adjacent frequencies for which the filter technology may be insufficient to prevent coexistence interference.
A mobile terminal in communication with a source access point, such as a source enhanced Node B (eNodeB), may determine one or more frequencies, such as a range of frequencies, that should be avoided in order to provide sufficient frequency separation so as to reduce the impact of coexistence interference. However, a mobile terminal may be handed over from the source access point that is currently serving the mobile terminal to a target access point, such as a target eNodeB, that will service the mobile terminal in the future. Following the handover, the information regarding the frequencies to be avoided in order to reduce coexistence interference may be lost such that coexistence interference may be greater following the handover than prior to the handover. Indeed, a ping-pong effect may occur in which a mobile terminal that has learned to avoid the use of a certain range of frequencies so as to maintain sufficient frequency separation while served by a source access point may begin using a frequency within the range while served by a target access point so as to again suffer from in-device coesistence interference.
For mobile terminals in an active mode, there are two types of handover procedures in an LTE network, namely, an X2-handover procedure and a S1-handover procedure. For intra-LTE mobility, the X-2-handover procedure is typically employed for an inter-eNodeB handover. However, in instances in which there is no X-2 interface between the eNodeBs or in an instance in which the source eNodeB has been configured to initiate a handover toward a target eNodeB via a S1 interface, a S1 handover will be triggered. Additionally, S1 handovers may be utilized between at least some home eNodeBs (HeNBs) such as in conjunction with Releases 8 and 9 of HeNBs and in instances in which the mobility management entity (MME) performs access control. While techniques have been proposed in order to make a target access point aware of the frequencies to be avoided in order to reduce the coexistence interference in conjunction with X2 handovers, this information is not shared during a S1 handover such that the target access point may utilize one of the frequencies that was being avoided by the source access point, thereby incurring coexistence interference.